Joel On Software
I don’t like very many usability or software blogs (mainly because most of the writers aren’t, and when they do explain things, it never seems to be in English), but I really like Joel on Software. He breaks software development and usability issues into nice, easy tidbits anyone can understand.
Many of the topics he covers I have no real interest in (SQL Server Mirroring? What the hell?), but the topics he does cover, like how improving software doesn’t mean a complete rewrite of such software, and usability for developers that don’t really care, are well written, thought out, and easy to read.
Some other software gurus (hey Dave Winer, you listening?) should take notice.